USN - The United States Navy is the branch of the United States armed forces responsible for conducting naval operations and is one of seven uniformed services. The 21st century United States Navy maintains a sizable presence in the world, deploying in such areas as East Asia, Southern Europe, and the Middle East. Its ability to project force onto the littoral regions of the world, engage in forward areas during peacetime, and rapidly respond to regional crises makes it an active player in American foreign and defense policy.